We are conducting research on methods for driving displays stably. The digital driving method supplies a constant current to the pixels and is able to stably display images with highly uniform brightness. However, the pulse width modulation method, which is widely used for displaying gradation in the digital driving method, suffers from problems of poor motion image quality, such as due to false contours, and that it is difficult to increase the frame rate. We therefore investigated pulse-density modulation for displaying gradation by controlling the light emission interval. Generally, the pulse-density modulation method requires a panel refresh rate of 15,000 Hz or more to achieve good image quality. We therefore investigated the relationship between panel refresh rate and image quality by using an image quality simulation. The results showed that good image quality can be obtained at a panel refresh rate of 1,920 Hz by using a random dither with a blue noise mask and a time sharing method. Additionally, the evaluation of the proposed method using a motion image quality simulation confirmed that motion image quality degradation issues such as false contours do not occur.
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